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MODBUS SYSTEM SET UP
This section describes the functioning of the Model 1700 controller and Model 1708/1716
RTUs in a MODBUS system.
MODBUS OPTION
The Model 1700 controller has an optional implementation of the industry standard
MODBUS protocol. This option is provided by means of a replacement EPROM containing
code to support the MODBUS protocol when communicating with the PC running the
MODBUS application. The Model 1708 and Model 1716 RTUs do not require any
modification to support the MODBUS protocol if they are communicating only with the
Model 1700. There are optional EPROMs for both of the RTU models that will allow them to
be interfaced directly to the PC, by-passing the Model 1700 controller. The MODBUS
implementation makes the devices compatible with nearly all SCADA programs as well as
with many PLCs.
The Model 1700 is compatible with most MODBUS programs that use five-digit MODBUS
addresses and limit themselves to the functions listed in Table 10.
Table 10. Compatible MODBUS Functions
MODBUS Function
Function Code
Used for...
Read Coil Status
01
Digital Outputs
Read Input Status
02
Digital Inputs
Read Holding Registers
03
Analog Outputs, Counters, Accumulators
Read Input Registers
04
Analog Inputs
Force Single Coil
05
Digital Outputs
Preset Single Register
06
Analog Outputs, Counters, Accumulators
Force Multiple Coils
0F
Digital Outputs
Preset Multiple Registers
10
Analog Outputs, Counters, Accumulators
The correspondence between Zetron and MODBUS I/O terminology is listed in Table 11.
Table 11. Zetron and MODBUS I/O Terminology
Zetron I/O Type
MODBUS I/O Type
Digital/Relay Output
Coil
Digital Input
Input Status
Analog Input
Input Register
Analog Output
Holding Register
Accumulator
Holding Register
Counter
Holding Register
Run-time
Holding Register
Содержание 1708
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Страница 60: ...Repair 025 9209K 60 MODEL 1700 SERIES ENCLOSURE OUTLINE 024 0057B...
Страница 61: ...Repair 025 9209K 61 MODEL 1700 SERIES ENCLOSURE INSTRUCTIONS 024 0056D Sheet 1 of 2...
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Страница 63: ...Repair 025 9209K 63 MODEL 1708 REMOTE TERMINAL UNIT SILKSCREEN 702 9439F...
Страница 64: ...Repair 025 9209K 64 MODEL 1716 REMOTE TERMINAL UNIT SILKSCREEN 702 9440F...
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